1. Field of the Invention
The present invention relates generally to mobile IP, and in particular to a support for multiple mobile IP sessions with dynamically allocated home IP addresses.
2. Description of the Related Art
CDMA2000 is a 3G mobile telecommunications standard in which the Packet Core Network (PCN) serves as the cornerstone that provides Internet Protocol (IP) services and mobile IP services to mobile nodes (MNs).
A CDMA2000 network comprises, at least logically, a Home Agent (HA), a Foreign Agent (FA), a Packet Data Serving Node (PDSN), and an Authentication, Authorisation and Accounting Server (AAA). The HA keeps track of the MNs associated with the network, among other things acting like a router when a MN roams in another network, receiving packets intended for the MN and tunnelling them towards the MN, via a FA in the network where the MN is located. The HA also provides mobile IP service to MNs together with a PDSN and the AAA server.
During mobile IP registration, a MN sends a mobile IP registration request to the HA, if necessary forwarded by the FA. The MN may request a dynamically allocated home IP address by setting the home IP address field in the request to zero, i.e. 0.0.0.0 for Internet Protocol (IP) version 4. The HA then dynamically allocates a home IP address for the MN and returns this to the MN in a mobile IP registration response, and the HA also creates a mobility binding that is the home IP address+the IP address of the FA, and the mobility binding is also associated with the Network Access Identifier (NAI) that was provided in the registration request. Thus, under the assumption that a MN only uses one NAI, if a MN has multiple mobility bindings, they are all associated with the same NAI.
During a PDSN to PDSN handoff, a MN sends a mobile IP registration request to update the mobility binding on the HA. If the registration request includes the home IP address, then the mobility binding is updated. This is usually the case as MNs usually remember the dynamically allocated home IP address after PDSN to PDSN handoff.
Some MNs may however forget their home IP address and therefore send a registration request with the home IP address field set to zero. This is not a big problem for present day HAs that only support single mobile IP sessions to MNs, regardless of whether or not the MNs forget the dynamically allocated home IP address at PDSN to PDSN handoff. In this case, if the HA has a mobility binding for the MN, then the HA finds the mobility binding and the previously allocated home IP address, which is returned to the MN in the registration response. If the MN really requests a new dynamically allocated home IP address, i.e. the HA does not have a mobility binding for the MN, then the HA dynamically allocates a new home IP address and returns this to the MN in the registration response.
However, a HA that supports multiple mobile IP sessions for a MN, i.e. a MN may negotiate multiple mobile IP sessions using the same NAI, the HA may encounter a hitherto unsolvable problem. Since one NAI may have multiple mobility bindings associated with it on the HA, how does the HA know what a second registration request with the home IP address field set to zero means? Is it a request for a second mobility binding, or did the MN forget its home IP address during PDSN to PDSN handoff?
It would be advantageous to have a method, a system and a HA that support for multiple mobile IP sessions for a MN, regardless of whether or not it forgets its home IP address during PDSN to PDSN handoff. The present invention provides such a method, system and HA.